Microfeature devices, such as semiconductor devices, imagers and displays, are generally manufactured on and/or in microfeature workpieces. A variety of chemical processes are used to manufacture and analyze (e.g., quality control testing) the microfeature devices. As feature sizes decrease and performance increases, it is becoming ever more important to control the composition of the materials. As such, microfeature workpieces are highly sensitive to variations or contamination during such chemical processes.
Etching is one common chemical process that is used in manufacturing operations. In a typical application, a workpiece may be etched to form vias, pattern a blanket conductive layer to form conductive lines, or form other structures on the workpiece. There are generally two types of etching processes—“dry” etching and “wet” etching. Most dry etching operations use a high-energy plasma that selectively removes portions of the microfeature workpiece. Wet etching processes generally immerse the workpiece in a tank that contains a liquid etching solution (i.e., an etchant).
FIG. 1 schematically illustrates a conventional wet etching system 10 in which a microfeature workpiece W is immersed in a processing fluid within a tank 20. The system 10 can include a fluid inlet 30 at a lower portion of the tank 20 for providing a flow 40 of processing fluid. The system 10 can further include a diffuser plate 50 having a plurality of apertures 52 positioned between the inlet 30 and the workpiece W. The diffuser plate 50 creates a more uniform flow of processing fluid across the workpiece W.
One problem with the conventional system 10 is that bubbles 42 entrained in the flow of processing fluid pass across the workpiece W. The bubbles 42 are typically generated by an impeller (not shown) that pumps the processing fluid, but they can also be generated by other parts of the system 10. The bubbles 42 in the flow 40 of the processing fluid tend to collect on a bottom surface of the diffuser plate 50 and migrate toward the perimeter of the diffuser plate 50. As the bubbles 42 move laterally across the diffuser plate 50, several bubbles 42 pass through the apertures 52 and across the workpiece W. The bubbles 42 that pass across the workpiece W interrupt the chemical reaction between the processing fluid and the workpiece W. This generally causes streaking defects across the surface of the workpiece W and/or otherwise damages the workpiece W. Accordingly, there is a need to improve the wet etching process to mitigate the effects caused by bubbles in the flow of processing fluid.